arXiv subjects

O. Sotolongo-Costa

Publications and source records attributed to O. Sotolongo-Costa.

26 records · Page 2Linked to original sources

arXiv2002

Levy Flights and Earthquakes

Levy flights representation is proposed to describe earthquake characteristics like the distribution of waiting times and position of hypocenters in a seismic region. Over 7500 microearthquakes and earthquakes from 1985 to 1994 were analyzed to test that its spatial and temporal distributions are such that can be described by a Levy flight with anomalous diffusion (in this case in a subdiffusive regime). Earthquake behavior is well described through Levy flights and Levy distribution functions such as results show.

cond-mat.soft↗

arXiv2002

Behavior of tumors under nonstationary theraphy

We present a model for the interaction dynamics of lymphocytes-tumor cells population. This model reproduces all known states for the tumor. Futherly,we develop it taking into account periodical immunotheraphy treatment with cytokines alone. A detailed analysis for the evolution of tumor cells as a function of frecuency and theraphy burden applied for the periodical treatment is carried out. Certain threshold values for the frecuency and applied doses are derived from this analysis. So it seems possible to control and reduce the growth of the tumor. Also, constant values for cytokines doses seems to be a succesful treatment.

math-ph↗

arXiv2002

A non extensive approach for DNA breaking by ionizing radiation

Tsallis entropy and a maximum entropy principle allows to reproduce experimental data of DNA double strand breaking by electron and neutron radiation. Analytic results for the probability of finding a DNA segment of length l are obtained reproducing quite well the fragment distribution function experimentally obtained.

cond-mat↗

arXiv1999

Universality classes in the random-storage sandpile model

The avalanche statistics in a stochastic sandpile model where toppling takes place with a probability p is investigated. The limiting case p=1 corresponds to the Bak-Tang-Wiesenfeld (BTW) model with deterministic toppling rule. Based on the moment analysis of the distribution of avalanche sizes we conclude that for 0<p<p_c the model belongs to the DP universality class while for p_c<p<1 it belongs to the BTW universality class, where p_c is identified with the critical probability for directed percolation in the corresponding lattice.

cond-mat↗

arXiv1999

Force fluctuations in granular materials

Force fluctuations in granular materials are investigated. A continuum equation is derived starting from a discrete model proposed in the literature. The influence of boundary conditions is investigated. For periodic boundary conditions the average weight is found to increase linearly with depth while it saturates to a constant value for absorbing boundary conditions, which models the existence of walls. The scale dependencies of the saturation weight, the saturation depth and the average squared fluctuations are obtained. The analytical results are compared with previous works and with numerical simulations in one dimension.

cond-mat↗

arXiv1998

Dynamic percolation and Slow Relaxation in Glass-like Materials

Glass-like materials are nonequilibrium systems where the relaxation time may exceed reasonable time scales of observations. In the present paper a dynamic percolation model is introduced in order to explain the principal properties of glass-like materials near the dynamic transition. Here, contrary to conventional percolation problems, clusters are groups of particles dynamically correlated. Introducing a size dependent relaxation time and the scaling hypothesis for the distribution of dynamically correlated clusters the two step relaxation predicted by the mode coupling theory and observed in experiments is obtained.

cond-mat↗

arXiv1997

Transition to self-organized criticality in a rice-pile mode

The self-organized critical state is characterized by a power law distribution of cluster sizes and other properties. However experiments with sand and rice piles reveal distributions of avalanche sizes which are not power law distributed. In the present letter a one-dimensional rice-pile model which demonstrate that this is only an apparent contradiction is introduced. Moreover, a robustness of the self-organized critical state is obtained with increasing system size.

cond-mat↗

arXiv1997

Sandpile Model for Relaxation in Complex Systems

The relaxation in complex systems is in general nonexponential. After an initial rapid decay the system relax slowly following a long time tail. In the present paper a sandpile modelation of the relaxation in complex systems is analysed. Complexity is introduced by a process of avalanches in the Bethe lattice and a feedback mechanism which leads to slower decay with increasing time. In this way, some features of relaxation in complex systems: long time tails relaxation, aging, and fractal distribution of characteristic times, are obtained by simple computer simulations.

cond-mat↗